1. Field of the Invention
The present invention relates generally to the field of cable connectors. More specifically, the present invention relates to a modular plug for terminating electric wires within a cable, such as round cables or any type of cordage carrying conductor pairs.
2. Description of the Background Art
In the telecommunications industry, modular plug type connectors are commonly used to connect customer premise equipment (CPE), such as telephones or computers, to a jack in another piece of CPE, such as a modem, or in a wall terminal block. These modular plugs terminate essentially two types of cable or cordage: ribbon type cables and round cables.
In ribbon type cables, the conductors running therethrough are arranged substantially in a plane and run, substantially parallel, alongside each other throughout the length of the cable. The individual conductors may have their own insulation or may be isolated from one another by channels defined in the jacket of the ribbon cable itself, with the ribbon jacket providing the necessary insulation. Conversely, the conductors packaged in a standard round cable may take on a random or intended arrangement with conductors being twisted or wrapped around one another and changing relative positions throughout the cable length.
Traditional modular plugs are well suited for terminating ribbon type cables. Typically, these plugs are of a dielectric, such as plastic, structure in which a set of terminals are mounted side by side in a set of troughs or channels in the plug body such that the terminals match the configuration of the conductors in the cable connected thereto. When the plug is inserted into a jack, the terminals electrically engage jack springs inside the jack to complete the connection.
On the other hand, termination of standard round cables or cords poses unique assembly problems for the skilled technician. For example, termination of a round cable carrying, for example, four conductor pairs by means of an existing modular plug requires the following steps: First, the cable or cord jacket must be stripped to access the enclosed conductors. Next, because the conductors in a conductor pair are generally twisted around one another, the twist must be removed and the conductors oriented to align with the required interface. For some standardized plugs, aligning the conductors also involves separating the conductors in at least one of the pairs and routing these over or under conductors from other pairs while orienting all the conductors in a side-by-side plane, thus, the orientation process can result in various conductors of different pairs crossing over each other, thereby inducing crosstalk among the several conductor pairs.
Crosstalk is defined as the cross coupling of electromagnetic energy between adjacent conductor pairs in the same cable bundle or binder. Crosstalk can be categorized in one of two forms: Near End Crosstalk, commonly referred to as NEXT, is the most significant because the high energy signal from an adjacent conductor can induce relatively significant crosstalk into an attenuated receiver signal. The other form is Far End Crosstalk or FEXT. FEXT is typically less of an issue because the far end interfering signal is attenuated as it traverses the loop. Because the jack springs, conductors and the plug terminals or contacts near the jack springs are generally quite close to, and exposed to, one another in a communication plug, control of crosstalk is a paramount consideration in any plug design. Unfortunately, crosstalk in a communication plug cannot be merely eliminated. Jacks are engineered to generate a certain amount of compensating crosstalk to counter the crosstalk produced in the plug. Accordingly, a communication plug should be designed to “optimize” rather than to minimize crosstalk. The term “optimize” is meant to convey that the crosstalk induced in a plug is controlled, and hence constant as compared to any other plug. Hence, if the induced NEXT in a plug is predictable, the jack can be accurately designed to compensate for that the anticipated NEXT induced in the plug.
In modular plugs currently in use, when the conductors are untwisted and inserted into the front of the plug housing, it is difficult to control their lengths, which, in turn, causes variation in electrical performance. This lack of precise control also leads in variations in electrical performance from plug to plug, whereas reproducibility of performance is a desideratum. In addition, an anchor bar is generally used to hold the cord or cable in the housing, and thereby provide strain relief. However, the anchor bar deforms the cable and introduces a random variable in performance, which is caused by the conductors being forced together at different stages of their twist. As a consequence, it is difficult to predict a plug's electrical characteristics, and the high degree of variability can result in reduced signal carrying performance in at least some of the circuits. This problem is discussed fully in U.S. Pat. No. 6,056,586 of Lin, issued May 2, 2000, the disclosure of which is herein incorporated by reference.
Also, in some current high frequency communication plugs, the conductors are terminated in the middle of the plug by insulation displacement connectors. The materials cost of the plug is greatly increased due to the amount of material such as phosphor bronze required by this type of structure. Also, in such a plug, the overall dimensions of the plug are increased, which hinders or prevents use of the plug in a confined place, such as high-density network hubs.
In addition, the technician time involved in the prior art practice of separating out the twisted pairs of conductors and routing them to their proper terminals in the plug is considerable. Even if the technician, splicer, or other assembly person is accurate in the disposition of the conductors, the time consumed by him or her in achieving such accuracy is considerable. Thus, the time spent in properly routing the conductors can add considerable cost. When it is realized that thousands of such connections are made daily, involving at least hundreds of technicians, it can be appreciated that any reduction in time spent in assembling the plug can be of considerable economic importance.
Accordingly, there exists a need for a modular plug that can terminate a standard round cable and that provides a straightforward interface between the conductors in the cable and the plug terminals, that involves less assembly time than heretofore, and which has substantially unvarying electrical characteristics from plug to plug.
One step toward achieving these goals is disclosed in U.S. Pat. No. 6,250,949 of Lin, issued Jun. 26, 2001, the disclosure of which is herein incorporated by reference. U.S. Pat. No. 6,250,949 provides a modular plug that can be easily assembled by a technician. The plug includes a conductor organizing sled, which controls the routing and placement of the twisted pairs of conductors inside the plug. The conductor organizing sled helps to ensure that the lengths of the individual conductors, and relative placements of the individual conductors, inside the plug is relatively consistent from plug to plug. Hence, the plug design disclosed in U.S. Pat. No. 6,250,949 helps to “optimize” the NEXT, so that the NEXT of the plug can be effectively reduced by a NEXT compensation scheme within a jack.
Such a plug has been well accepted in the industry and vastly employed. At CAT 5 standards, the plug design is completely acceptable at keeping NEXT within an acceptable level. However, there is always a trend toward faster transmission speeds and a further reduction of NEXT, such that future plug/jack combinations will need to reduce NEXT even further as performance standards increase (such as the minimum performance characteristics defined by future CAT standards).